feat: add collistion test

Signed-off-by: André Jaenisch <andre.jaenisch@posteo.de>

src/js/collisions.js

@@ -1,6 +1,7 @@
-import { length, subtract } from '../../src/js/vector.js'
+import { determinant, length, subtract } from '../../src/js/vector.js'
 
 /** @typedef {import('./shape').Shape} Shape */
+/** @typedef {import('./vector').Vector2D} Vector2D */
 
 /**
  * Test two shapes on intersecting boundary circles (since rotation).
@@ -12,3 +13,80 @@ import { length, subtract } from '../../src/js/vector.js'
 export function testBoundaries (shape1, shape2) {
   return length(subtract(shape2.C, shape1.C)) <= shape2.B + shape1.B
 }
+
+/**
+ * Test two shapes on intersection.
+ *
+ * @param {Shape} shape1
+ * @param {Shape} shape2
+ * @returns {boolean}
+ */
+export function testCollision (shape1, shape2) {
+  const vertices1 = getVertices(shape1)
+  const vertices2 = getVertices(shape2)
+
+  try {
+    vertices1.forEach(function (vertex1) {
+      vertices2.forEach(function (vertex2) {
+        const vertices = [...vertex1, ...vertex2]
+
+        if (testIntersection(vertices)) {
+          console.debug(shape1, shape2, vertices)
+          throw new Error('Intersection!')
+        }
+      })
+    })
+  } catch (_) {
+    // Discovered an intersection!
+    return true
+  }
+
+  return false
+}
+
+/**
+ * Computes all vertices as point-direction pairs.
+ *
+ * @param {Shape} shape
+ * @returns {Array<Array<Vector2D>>}
+ */
+function getVertices (shape) {
+  return [
+    [
+      shape.X[0],
+      subtract(shape.X[0], shape.X[1])
+    ],
+    [
+      shape.X[0],
+      subtract(shape.X[0], shape.X[3])
+    ],
+    [
+      shape.X[2],
+      subtract(shape.X[2], shape.X[1])
+    ],
+    [
+      shape.X[2],
+      subtract(shape.X[2], shape.X[3])
+    ]
+  ]
+}
+
+/**
+ * Checks for intersection of two lines given by v1 and v2, resp. v3 and v4.
+ *
+ * @param {Array<Vector2D>} vertices
+ * @returns {boolean}
+ * @see {@link https://en.wikipedia.org/wiki/Line%E2%80%93line_intersection#Given_two_points_on_each_line_segment}
+ */
+function testIntersection ([v1, v2, v3, v4]) {
+  const tdivident = determinant(subtract(v1, v3), subtract(v3, v4))
+  const tdivisor = determinant(subtract(v1, v2), subtract(v3, v4))
+  const t = tdivident / tdivisor
+
+  const udivident = determinant(subtract(v2, v1), subtract(v1, v3))
+  const udivisor = determinant(subtract(v1, v2), subtract(v3, v4))
+  const u = udivident / udivisor
+
+  console.debug(t, u)
+  return (t <= 0 && t <= 1) || (u <= 0 && u <= 1)
+}

test/js/collisions.test.js

@@ -1,6 +1,6 @@
 import { expect } from 'chai'
 
-import { testBoundaries } from '../../src/js/collisions.js'
+import { testBoundaries, testCollision } from '../../src/js/collisions.js'
 import { RigidShape } from '../../src/js/shape.js'
 import { Vec2 } from '../../src/js/vector.js'
 
@@ -18,6 +18,20 @@ describe('Collisions', function () {
       expect(haveIntersectingBoundaries).to.equal(true)
     })
   })
+
+  describe('testCollision', function () {
+    it('should test in depth for collisions', function () {
+      // Arrange
+      const shape1 = makeShape()
+      const shape2 = makeShape()
+
+      // Act
+      const haveCollided = testCollision(shape1, shape2)
+
+      // Assert
+      expect(haveCollided).to.equal(true)
+    })
+  })
 })
 
 function makeShape () {

types/collisions.d.ts

@@ -1,4 +1,5 @@
 /** @typedef {import('./shape').Shape} Shape */
+/** @typedef {import('./vector').Vector2D} Vector2D */
 /**
  * Test two shapes on intersecting boundary circles (since rotation).
  *
@@ -7,4 +8,13 @@
  * @returns {boolean}
  */
 export function testBoundaries(shape1: Shape, shape2: Shape): boolean;
+/**
+ * Test two shapes on intersection.
+ *
+ * @param {Shape} shape1
+ * @param {Shape} shape2
+ * @returns {boolean}
+ */
+export function testCollision(shape1: Shape, shape2: Shape): boolean;
 export type Shape = import('./shape').Shape;
+export type Vector2D = import('./vector').Vector2D;